1. Field of the Invention
The present invention relates to a method and apparatus for processing a weft suffering abnormal insertion and beaten into woven fabric so as to be removed therefrom.
2. Description of the Prior Art
When abnormal insertion of a weft occurs in a jet loom, operation of the latter is stopped in response to a detection signal outputted from a weft detector and indicating the abnormal weft insertion. In the case of a jet loom operating at a high speed, the loom is stopped only after allowing one or more rotations of the loom crank shaft under inertia. Attempts to stop the loom abruptly are avoided because of the possibility that the components of the loom might be subjected to damaging stress. Consequently, the weft suffering the abnormal insertion (hereinafter referred to as defective or faulty weft) will have been beaten up to a fell of cloth or woven fabric at a time point immediately preceding complete stopping of the jet loom.
In this conjunction, a weft processing apparatus designed for removing such faulty weft as mentioned above which would otherwise involve a defect in the woven fabric is disclosed in Japanese Laid-Open Patent Application Nos. 170556/1987 (JP-A No. 62-170556), 206058/1987 (JP-A No. 62-206058) and 245339/1986 (JP-A No. 61-245339) and Japanese Laid Open Utility Model Application No. 41083/1987 (JP-A No. 62-41083U). In the case of these prior art apparatuses, succeeding insertion of a weft is inhibited when the loom is stopped upon occurrence of the abnormal weft insertion, while a woven weft cutter apparatus disposed in association with a weft inserting main nozzle is simultaneously set to the inoperative state, whereby the faulty weft beaten up to the fell of cloth can be laterally withdrawn for removal from the weft inserting main nozzle by making use of the weft leading to the woven fabric as a clue. More specifically, the weft serving as a clue is introduced not only into a guide cylinder disposed above the weft inserting main nozzle through the medium of a jet stream produced by a blow nozzle, but also into a housing disposed orthogonally to the abovementioned guide cylinder to be subsequently wound up by a winding apparatus installed within the housing, whereby the faulty weft is withdrawn from the cloth fell to be removed. Thereafter, on the basis of a detection signal produced within a predetermined time by a weft detector mounted inside of the guide cylinder and indicating the presence or absence of the weft, decision is made as to whether the disposal or processing of the faulty weft has been conducted successfully or not. In the case of the arrangement disclosed in JP-A No. 62-170556, the amount of rotation of taking-over or withdrawing rollers provided in a pair is measured by means of a contactless switch, while in the apparatus disclosed in JP-A No. 62-206058, the amount of rotation of a length measuring roller is determined in the similar manner and taken into account in making a decision concerning the disposal of the faulty weft.
It is however noted that the faulty weft being wound up by the weft winder disposed within the housing by way of the guide cylinder is bent approximately at a right angle at an end of an upper group of warps forming a shed. In that case, the bending of the weft encounters resistance of great magnitude and is likely to bring about breakage of the weft on the way to the weft winder. The possibility of such breakage is significantly high in the case of the weft which is relatively feeble by nature. Thus, the ratio of failure in disposing of the faulty weft is increased to lower the operation efficiency of the jet loom, providing an obstacle to the inherently high productivity thereof.
Further, in the case of the apparatus disclosed in JP-A No. 62-170556 and JP-A No. 62-206058, there are required detecting and/or measuring means such as a rotary encoder, contactless switch, a timer or the like for detecting the amount of rotation of a winder driving motor or the roller in conjunction with the decision concerning the result of the weft disposal operation. Apparently, the presence of such measuring means will increase the ratio at which erroneous operation takes place because of false measurement. By way of example, decision of the unsuccessful weft disposal may be made notwithstanding of the successful operation and vice versa. Such erroneous decision will result in the unnecessary shut down or stoppage of the loom, leading to lowering of the operation efficiency thereof or such inconvenience that the faulty weft is left in the shed formed by the warps.
As the detector for detecting the presence or absence of the weft in the guide cylinder within a predetermined time, there is commonly employed a photoelectric type weft detector. Further, in the apparatus disclosed in Japanese Laid-Open Utility Model Application No. 46676/1987 (JP-A No. 62-46676), such arrangement is adopted in which a weft detector provided with a rotatable detecting arm is translated, following up the movement of one of the paired weft taking-over rollers for engaging the other under pressure, wherein the rotatable detecting arm sweeps transversely the weft transfer path.
The photoelectric weft detecting device is however disadvantageous in that vibration of the weft being transferred to the weft taking-over means may bring about error, degrading the accuracy at which the absence or presence of the weft is detected, which in turn increases undesirably the probability of the erroneous decision concerning the disposal of the weft. In the case of the mechanical weft detecting operation with the aid of the rotatable detecting arm, degradation in accuracy of detection due to the vibration of the weft can certainly be avoided. However, in the translation type detection system in which the detecting member of the weft detector is caused to move in parallel in accompanying the movement of the gripping rollers, the detecting arm has to perform the sweeping operation across the relatively wide weft transfer path wholly. In that case, the range in which the detecting arm can be rotated may be restricted or narrowed under constraint exerted by the weft engaging the detecting arm, which will possibly result in that ON/OFF operation of the weft detector can no more be effectuated notwithstanding the presence of the weft.
Besides, in the apparatus disclosed in JP-A No. 61-245339 and JP-A No. 62-41083U mentioned above, the jet stream produced by the blow nozzle and directed to the guide cylinder can not be avoided from diffusion, lowering the reliability of introducing into the guide cylinder the weft that follows the faulty one, and resulting in frequent failure in transferring the weft from the blow nozzle to the weft winder. As a result, the probability of unsuccessful processing or disposal of the faulty weft is increased, leading to lowered operating efficiency and making it difficult to attain the high yield otherwise afforded by the jet loom. Additionally, although the blow nozzle for blowing the weft toward the guide cylinder, and the weft inserting main nozzle, are mounted in fixed relative position to ensure positive prevention of the weft insertion, the weft inserting main nozzle and the guide cylinder are moved relative to each other during inertial operation of the loom occuring subsequently to detection of the faulty weft insertion. This is due to the fact that the guide cylinder for introducing the succeeding weft to serve as the clue for withdrawing the faulty weft, is fixedly mounted on the base portion of the loom. Consequently, reliability can not be assured in the transfer of the weft between the weft inserting main nozzle and the inlet port of the guide cylinder, resulting in an increase in the probability of failure in the disposal of a faulty weft.
Further, with the arrangement in which the tip portion of the weft is introduced into the housing disposed approximately orthogonally to the direction in which the weft is delivered from the guide cylinder, as disclosed in JP-A No. 61-245339 and JP-A No. 62-41083U, introduction of the weft to the weft winder can not be realized positively, involving high ratio of failure in the transfer of the weft from the taking-up means to the winder. As a result, the ratio of failure in the disposal of the faulty weft is increased, preventing the inherent high productivity of the jet loom from being fully achieved.
As is apparent to those skilled in the art, there exists thus a need for the faulty weft disposal method and apparatus which are substantially immune to the shortcomings of the prior art elucidated above.